It has been proposed to provide an air-bag located in front of a passenger in a motor vehicle, the air-bag being arranged to be inflated in case of an impact involving the vehicle to provide protection for the occupant.
It is known that whilst such an air-bag may provide good protection for a seat occupant who, at the instant of impact, is sitting in an “ordinary” position, nevertheless, the air-bag may not operate optimally for a seat occupant who, at the moment of impact, is not in the ordinary position, but, instead, is leaning forwards, for example to gain access to a glove box.
It has been proposed that an arrangement should be provided to detect when a vehicle occupant is out of the ordinary position and to moderate inflation of the air-bag, or even inhibit inflation of the air-bag, in such a situation.
Various proposals have been made previously concerning detectors to detect when a vehicle occupant is out of position. Suggestions have been made involving the use of capacitative sensors, the electric capacity of such sensors depending upon the proximity of various parts of the occupant. It has also been proposed to use various sensors which use transmitted waves, such as infrared or ultrasonic sensors, with the sensors being used in the manner of a radar or “echo sounder” to determine the position of the occupant. Such sensors are expensive, or complicated, or unreliable.
It has also been proposed to utilise a sensor which determines the length of the safety belt, as worn by the vehicle occupant, that has been withdrawn from the retractor on which the safety belt is initially stored. However, even a sensor of this type does not, of itself, provide a reliable indication of the position of the occupant.
The present invention seeks to provide an improved safety device.
According one aspect of this invention there is provided a safety arrangement for detecting the position of an occupant of a seat in a motor vehicle, the seat being provided with a safety belt and an associated retractor for use by the occupant of the seat, there being a sensor for measuring a parameter corresponding to the length of belt withdrawn from the retractor relative to a predetermined reference value, the safety arrangement also incorporating a seat position sensor and a processor unit to process signals from the two sensors to evaluate the position of the seat occupant, wherein the safety belt system incorporates a buckle, the buckle being provided with a sensor to indicate when the safety belt is buckled in position, the predetermined reference value being the minimum belt length remaining withdrawn from the retractor after the belt has been buckled up.
Preferably the processor unit utilises signals from the seat position sensor to determine the ordinary position of the front part of the chest bone of a seat occupant relative to an air-bag, that position corresponding to the predetermined reference value of belt length.
According to another aspect of this invention there is provided a safety arrangement for detecting the position of an occupant of a seat in a motor vehicle having a fixed position, the seat being provided with a safety belt and an associated retractor for use by the occupant of the seat, there being a sensor for measuring a parameter corresponding to the length of belt withdrawn from the retractor relative to a predetermined reference value. The safety arrangement also incorporating a processor unit to process signals from the sensor to evaluate the position of the seat occupant, wherein the safety belt system incorporates a buckle, the buckle being provided with a sensor to indicate when the safety belt is buckled in position, the predetermined reference value being the minimum belt length remaining withdrawn from the retractor after the belt has been buckled up.
Preferably the processor unit, based on the position of the seat, determines the ordinary position of the front part of the chest bone of a seat occupant relative to an air-bag, that position corresponding to the predetermined reference value of belt length.
Conveniently the reference value is continuously or repeatedly updated, and a new reference value is stored whenever a new minimum belt length remaining withdrawn from the retractor, which is less than the current minimum length, is determined.
Advantageously a measured change in the length of the belt withdrawn from the retractor, relative to the predetermined reference value is utilised, by the processor unit, to estimate the longitudinal change in position of the front part of the chest bone of the seat occupant.
Preferably the parameter that is measured is the extent of the angular rotation of the spool of the seat belt retractor.
In one embodiment the processor unit is connected to control the performance of a load-limiter for the safety-belt.
In a preferred embodiment the processor unit is connected to an air-bag unit positioned in front of the vehicle seat to control the mode of performance of the air-bag.
Conveniently the processor unit modifies the venting of the air-bag.
Alternatively the processor unit moderates deployment of the air-bag.
Alternatively again the processor unit inhibits deployment of the air-bag.
Preferably the processor unit is configured to determine a new reference value whenever the seat is moved after the predetermined reference value has been determined.
Advantageously the new reference value is determined by determining the minimum length of belt withdrawn from the retractor after the seat is moved, the processor being configured to process signals corresponding to the new minimum belt length and the new position of the seat.
Preferably the new reference value is determined by determining the change in the position of the seat and modifying the original predetermined reference value.
Conveniently the reference value is modified by a value corresponding to the distance of, and the direction of, the change in position of the seat.
Conveniently subsequently a new reference value is determined by determining the minimum length of belt withdrawn from the retractor and the position of the seat.